Not too long ago, one who needed computing was required to send one's work to a central computer facility. With the advent of microprocessors, however, a user can communicate with a large computer using an intelligent terminal. At any time, there exist many such users who may be competing with one another to access the computer. Some of these users may take longer than others. Among the others, however, there may be some who need relatively shorter access times. The users are typically queued behind one another in their order of arrival. If a user needing a longer access time should be ahead of several needing relatively shorter access times, there latter users may have to wait a long time. This problem is known as delay or queuing. Many solutions have been proposed. An introduction to this may be found in a book entitled, COMPUTER NETWORKS by A. S. Tanenbaum, published in 1981 by Prentice-Hall, Inc.
Often, these users need to communicate with one another. A switch, located at a node, interconnects one user's terminal equipment with another user's terminal equipment. These terminals may be intelligent terminals, computers, or the like. A method for sending the information from one terminal to another is by way of packets. One system called DATAKIT VCS, a trademark of the AT&T Co. is disclosed in a paper by Mr. A. G. Fraser published by the International Conference on Communications, Boston, MA, 1979, volume 2, pages 20.1.1 to 20.1.3. A widely accepted specification for sending data in packets is found in a book published by the International Telecommunications Union, Geneva, 1977, entitled PUBLIC DATA NETWORKS, volume V111.2, authored by The International Telegraph and Telephone Committee (CCITT).
Sometimes, a user served by a first node may want to communicate with another user served by a second node. This second node is often located in the same business complex and connected with the first node by a light fibers. If, however, as is increasingly common, the second node is located at a distance from the first node, beyond the availability of light fibers, the two nodes can only be interconnected by currently available facilities. Generally available facilities in the United States can convey data only at a speed of fifty-six kilo bits a second.
It becomes apparent then that an algorithm is needed for sending data in packets between two terminals served by nodes separated by some distance using currently available slower facilities. Furthermore, this algorithm should insure that because slower facilities are used, no user should delay other users served by the same node.